The mechanical advantage of a simple machine can be predicted by comparing input and output distances. However, when the machine creates friction, the actual mechanical advantage is reduced. Efficiency can be calculated by dividing the actual mechanical advantage by the theoretical mechanical advantage. A machine that looks like it will give you a MA of 4 will only give an MA of 2, if friction lowers the efficiency to 50%.
We looked at this in the context of pulleys, where a range of MAs is easy to produce, but every increase in MA also brings more friction into the machine.
We looked at this in the context of pulleys, where a range of MAs is easy to produce, but every increase in MA also brings more friction into the machine.